Hatchability of the eggs laid by the hens fed a diet containing 15% of yeast grown on n-paraffin was tested to study the effect of vitamin B₁₂ injected to the hens at various levels. Ten lots of 10 hens each were fed the yeast diet without supplemental vitamin B₁₂ and two lots of 10 hens each were fed a control diet. After 5 weeks on the yeast diet, 0, 0.09, 0.18, 0.36 and 0.72μg of vitamin B₁₂/hen/day was injected every other day to the hens of to lots each. The eggs laid at the second week on vitamin B₁₂ injection were set in an incubator.
Number of chicks died in the egg shell before hatch was significantly more on the yeast diet without vitamin B₁₂ injection than that on the control diet.
Injection of vitamin B₁₂ was effective to prevent mortality of the chicks in the egg shell. Following linear regression was found fit to describe the relationship,
y=19.554-19.774x
where, x is μg of vitamin B₁₂ injected per head per day, and y is arcsin √percentage of mortality of the chicks in the shell. Correlation coefficient betmeen x and y was -0.7242, which was highly significant at 1% level.
Minimum amount of vitamin B₁₂ to be injected to prevent mortality of the chiks in the egg shell before hatch is estimated to be 0.99μg/head/day with 95% confidence interval of 1.79-0.72μg. Adding the amount of vitamin B₁₂ supplied through the diet daily, minimum requirement of vitamin B₁₂ of the breeding hens on the yeast is estimated to be 1.52μg/hen/day, which corresponds to 14.8μg/kg diet. The requirement is higher than that in Japanese Feeding Standard, and possible relationship with meta bolism of odd-numbered fatty acids rich in the yeast is discussed.

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Total 160 and 20 offspring of White Leghorn hens fed a breeder diet containing 15% of yeast grown on n-paraffin and a control breeder diet, respectively, were fed experimental starter diets containing graded levels of vitamin B₁₂ to study the effect of the breeder diet and of supplemental vitamin B₁₂ in the starter diet on the growth of the chicks.
The eggs for the offspring were collected at the second and the fourth week after feeding the breeder diets and incubated, respectively. Two lots of either 5 males or 5 females each on the yeast breeder diet were fed one of 8 starter diets and 2 lots of either 5 males on 5 females each on the control breeder diet ware fed the basal starter diet for 3 weeks in each of the two hatches. To the basal starter diet, containing 37.2% of the yeast, 0, 1.16, 2.31, 3.47, 4.62, 5.78, 6.94 and 8.09μg of vitamin B₁₂ per kg of diet was supplemented. Vitamin B₁₂ content in the supplement and in the basal starter diet was determined microbiologically.
Following Equation 2 was found fit to describe the linear relationship between supplemental vitamin B₁₂ and growth of the offspring on the yeast breeder diet,
y=44.60+0.518x (2)
where, x is supplemented vitamin B₁₂ (μg/kg diet) and y is body weight gain for 3 weeks per 100g of diet (g/100g).
Substituting the body weight gain of the offspring on the control breeder diet per 100g of the basal starter diet, i.e., 47.9g/loog, to y, the differnce between amounts of vitamin B₁₂ carried over from the hens on either the control or yeast breeder diet was estimated to be 6.37μg/kg of starter diet, which corresponded 1.7μg of vitamin B₁₂ per chick.
Requirement of vitamin B₁₂ for the chicks on the yeast breeder diet and fed the yeast starter diet was estimated to be 11.4μg/kg of starter diet with 95% confidence interval of 18.6-9.4μg/kg.

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The collavolative experiment was carried out to study the effect of age of chickens on fat content in abdomen, chemical composition in leg muscle and the taste of meat.
Experimental chickens (Hubbard) which hatched at 2 weeks intervals were reared by practical soybean-corn type diet. At 6, 8, 10, 12 and 14 weeks old, they were sacrificed at the same time.
It was observed that there were high correlations between age of chickens abdominal fat (male: r=0.965, female: r=0.998). With age of chikens, the content of moisture in leg musle linearly decreased, and on the contrary fat content increased. Correlation coefficients between moisture and fat content in female were -0.979 and 0.983, respectively. Also the contents of crude protein, inosinic acid and thickness of fiber in muscle were tended to increase with age of chickens.
In sensory test, steamed thigh muscle with common salt was used. Younger broiler meat was clearly felt to be softer smell and more tasteful. On the whole, panerists showed that softer meat was better, namely younger broiler was better.

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To clarify the incidence of avian infectious bronchitis (IB) in the field and serological types of IB virus, surveys of virus neutralizing (VN) antibodies were performed on chickens in Tottori prefecture. The results are as follows.
1. For the VN test, four strains of IB virus, Beaudette-42, KH (isolated in Japan), Holte and A-5968 were used as antigens. Consequently, in six of eleven flocks examined, the antibodies against one to four IB viruses used were demonstrated.
2. Four stocks showing some clinical signs, from two of which IB viruses were isolated, were immune to viruses used.
3. Out of the six immune flocks, five showed high VN titer to the Massachusettstype viruses. Thus this type of virus may have been distributed predominantly in this area. Moreover it was considered that the Connecticut-type virus affected the remaining one flock.
4. When investigations on the distribution of neutralizing antibodies against IB virus are performed, IB viruses of different serological types should be used as antigens.

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With the progress of mass raising of chicks, the wing-web-stab fowl pox vaccine has been applied more frequently than the feather-follicle vaccine. The stab vaccines have been used for the day-old broiler chicks, but recently the vaccines showed a bad take and poor immunity in some of broiler farms.
The present research reported here was carried out to clarify the bad take phenomenon of the stab vaccine.
Total 805 day-old male chicks of the Singlecomb White Leghorn were used in these investigations during 2 years from 1972 to 1973.
Three vaccines used were: A (attenuated fowl pox virus, strain B.) and B (pigeon pox virus, strain Nakan-K III) by the stab method, and feather-follicle vaccine (pigeon pox virus, strain Nakano).
The principal results obtained were as follows:
When the breeding stocks were immunized by the feathe-follicle vaccine, the dayold chicks were given a good take by A and B stab vaccines.
From the view point of good eruption formation in day-old chicks vaccinated percentage of take seemed to be lower in A stab vaccine than B when B stab vaccine had been applied for the breeding stocks. However, no difference of statistically significant was observed between A and B stab vaccines.
On the other hand, when the breeding stocks were immunized by A stab vaccine, the day-old chicks were given a good take by B stab vaccine, and A stab vaccine showed apparently lower percentage of take than B.

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[in Japanese]

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